1. Field of the Invention
The present invention relates to a method of controlling brush rotation in a cleaning device of an image forming system, in which a brush is made to rub against the surface of a photoreceptor so as to scrape off toner or talc adhering to the surface of the photoreceptor.
2. Description of the Related Art
FIG. 7 is a schematic view illustrating the configuration of a laser printer using an electrostatic copying machine. In the laser printer, an image signal transmitted from an external equipment (not shown) such as a computer or a word processor forms a latent image on a photoreceptor 5 by means of a laser light 4 incident through an optical system 3 including a polygon mirror 2. This latent image is developed in a developing device 6 and then transferred by means of a transfer portion 9 onto paper 8 fed from a paper feeding device 7.
The paper 8 carrying a toner image transferred thereto is fed to a fusing device 11 by means of a transport 10, and the paper 8 fused therein through heating is then discharged.
A cleaning device 12 is constituted by a brush 13 which is in contact, while rotating, with the rotating photoreceptor 5, a doctor blade 14 which is provided on the downstream side of the brush 13 so as to contact with the surface of the photoreceptor 5 in the direction opposite to the rotating direction of the photoreceptor 5, an auger 15 which discharges toner scraped from the photoreceptor 5, a housing 16 which houses the members described above, and so on.
The above-mentioned photoreceptor 5 is supported by a frame (now shown) which is provided integrally with the housing 16 of the cleaning device 12, and the photoreceptor 5 and the cleaning device 12 are provided in the form of a cartridge so as to be removable from the copying machine body in the direction of pulling out. This cartridge is hereinafter referred to as a print cartridge.
The brush 13 provided in the cleaning device 12 having such a configuration as described above is a so-called disturber brush. The brush 13 has a configuration in which number of hairs 18, for example, 60,000 hairs per in.sup.2, are planted in a core material 17 as shown in FIG. 8. Each hair 18 is composed of a material such as a copolymer of polypropylene or acrylic resin and vinyl chloride. These hairs 18 of the brush 13 contact, while flexing, with the photoreceptor 5.
The hairs 18 of the brush 13 contacting with the photoreceptor 5 are therefore left as they are being flexed at the time of stoppage of the copying machine. Thus, because the hairs 18 of the brush 13 are left in a state that they are in contact with the photoreceptor 5 while contacting with the latter for a long time, they are transformed as shown in FIG. 9 so that a concave portion 19 is produced.
If the operation of copying is performed in a condition that such a concave portion 19 is formed, a fluctuation of velocity is caused in the photoreceptor rubbed by the brush as shown in FIG. 10, so that a stripe pattern generally called banding is produced in an image on the photoreceptor 5 to thereby cause a defect in copying.
As a conventional countermeasure thereto, the brush is arranged so that it can be retracted from the photoreceptor in an unused time thereof, or hairs of the brush are made thin enough to prevent banding.
In the former one of the above-mentioned conventional countermeasures, there have been not only a problem that the printer is expensive because of the complicated retractable arrangement of the brush but another problem that the retracting operation causes leakage of toner. In the latter, on the other hand there has been a problem that the function of scraping off toner or talc adhering to the photoreceptor 5 is weakened.